Field of the Invention
The present invention relates to multi-ply, bonded cookware having a central area of a cooking surface that has a higher level of thermal conductivity than a distal area of the cooking surface, as well as sidewalls of the cookware. A method for making the cookware using solid state bonding is also disclosed.
Description of Related Art
It has long been known to manufacture multi-layer bonded composite cookware in which various materials are joined together to combine the desired physical properties of each of the materials into a composite. For example, the corrosion resistance of stainless steel is ideal for the cooking surface as well as for the exterior surface of cookware; however, the thermal conductivity of stainless steel is not relatively high. On the other hand, aluminum and/or copper offer much higher thermal conductivities and have been bonded to stainless steel to provide well-known composite cookware items such as pots, pans, and the like. Multi-layer bonded cookware is known in the art, as shown in a number of patents, such as, for example: U.S. Pat. Nos. 4,246,045 and 4,167,606 to Ulam; and U.S. Pat. Nos. 8,133,596 and 6,267,830 to Groll. These patents demonstrate that the manufacture of multi-layer bonded cookware comprising stainless steel outer layers bonded to central layer(s) of a higher conductivity aluminum and/or copper is well known in the art. The bonding between layers of these different materials is commonly achieved by conventional roll-bonding techniques using strips of aluminum and/or copper, roll-bonded to outer strips of stainless steel. It is known that roll-bonding between copper, aluminum, and stainless steel layers is conventional in the art of making composite cookware.
A solid state bonding technique using high static pressure and heat applied over time to make a plurality of composite blanks of, for example, a combination of stainless steel-aluminum-stainless steel in the manufactured cookware, is disclosed in U.S. Pat. No. 9,078,539 to Groll et al. There is a need in the art for producing cookware made using solid state bonding techniques for reducing the weight and improving thermal characteristics of the cookware.